A number of companies manufacture a variety of voltmeters, including high-voltage meters. The high-voltage meters may be of the type generally called hot-stick voltmeters or hot-stick voltmeters/phasers. Prior art hot stick voltmeters used on power distribution and transmission systems use encapsulated high voltage resistors, a meter display and a cord to connect either to ground or to a second resistor stick. Voltmeters with only one resistor stick have a cord to connect to earth ground and can measure voltage from any energized conductor referenced to ground. This is known as phase-to-ground or line-to-ground voltage. Voltmeters with two resistor sticks can measure phase-to-ground voltage if the second resistor stick is connected to ground, or the voltmeters can measure phase-to-phase voltage if each resistor stick is connected to a second energized phase. Voltmeters of both types are presently manufactured by HD Electric Company, with both analog and digital displays.
An example of a dual display voltmeter is shown in U.S. Pat. No. 7,746,051 which is owned by HD Electric Company. In a first embodiment of the '051 invention, the voltmeter/phaser has first and second probes for respectively accessing spaced-part points in a circuit, with a voltage measurement circuit proximate to the first probe. A cable including a first conductor connects the first and second probes to each other and to the measurement circuit. First and second voltage display circuits are respectively associated with the first and second probes, the first display circuit being connected directly to the measurement circuit. The cable includes a second conductor connected between the voltage display circuits for conducting a display data signal from the first display circuit to the second display circuit to ensure that both display circuits display the same voltage value. In another embodiment of '051 invention, a voltmeter/phaser has first and second high-voltage probes for respectively accessing spaced-apart points in a high-voltage circuit, with a high-voltage measurement circuit proximate to one of the probes. A cable connects the first and second probes to each other and to the measurement circuit. First and second high-voltage display circuits are respectively associated with the first and second probes and are coupled to the measurement circuit. In the '051 invention, voltmeter/phaser measures and displays a voltage between spaced-apart points in a circuit. This is accomplished by electrically contacting the points respectively with first and second probes and providing a plural-conductor cable between the probes. The method further includes conducting a current between the probes through a first conductor of the cable, measuring the current and displaying an equivalent measured voltage value on the first display. A signal representative of the displayed value is conducted through a second conductor of the cable to a remote display at the second probe so that both displays show the same value.
With the '051 invention, the voltage displayed is by definition the voltage difference between the two phases. This display is inherently limited to the voltage magnitude difference and cannot measure the phase angle difference and display the phase-to-phase voltage. In addition, with the '051 invention, since the sticks are corded, and typical cord lengths are in the range of 15 to 25 feet, the cord limits the distance between which voltage measurements may be made.
A high voltage digital voltmeter and wireless phaser is provided herein which provides improvements to the existing prior art and which overcomes the disadvantages presented by the prior art. Other features and advantages will become apparent upon a reading of the attached specification, in combination with a study of the drawings.